Autonomous terrain sensing method for extraterrestrial micro patrol detector

Abstract

The invention discloses a terrain autonomous sensing method for an extraterrestrial micro patrol detector, and belongs to the technical field of deep space detector control. According to the method, a Tof camera is adopted to measure an actual depth value of a star catalogue under camera coordinates, a depth theoretical model of a detection area is constructed, and a theoretical depth value of the star catalogue under the camera coordinates is calculated; designing an obstacle detection criterion based on the obtained actual depth value and the theoretical depth value; and detecting the obstacle in the detection area according to the obstacle detection criterion, and identifying whether the obstacle is a bulge or a pit. Aiming at the problem that a tiny patroller is difficult to realize effective perception under limited resources, obstacle detection only by using distance measurement information under an extremely low visual angle is realized, and the requirements of tasks such as star catalogue patrolling detection are met.

Description

Technical Field

[0001] The invention relates to an autonomous terrain sensing method for an extraterrestrial micro-patrol probe, belonging to the technical field of deep space probe control. Background Art

[0002] In deep space exploration missions, patrol exploration is an effective way to achieve close-range detection and expand the detection range. Extraterrestrial surface exploration requires that the rover can safely drive in an unknown and complex surface environment and reach the designated target point on the ground to complete specific scientific exploration tasks. In order to meet the above mission requirements, the rover needs to realize functions such as posture determination, environmental perception, path planning, motion control and health management. Among them, environmental perception is the core capability that determines the level of autonomous intelligence, and it is also the key to affecting the safety of detection, because once entering dangerous terrain, it is very easy to cause damage to the rover.

[0003] At present, star map obstacle detection and identification mainly use active or passive optical sensors to capture star map terrain data, process it and convert it into a DEM elevation map with terrain features and slope information. The detection method based on active sensors mainly relies on equipment such as laser radar, which uses the radar to actively send information and determine the detailed three-dimensional elevation information of the detection area terrain through the return signal, thereby determining the obstacle danger area. Passive sensors such as optical cameras have the characteristics of small size, light weight, low cost and low energy consumption. They mainly extract the relevant features of obstacles from two-dimensional images through feature extraction algorithms for detection. For future micro-rover detection missions, due to the constraints of weight, power consumption and harsh environment, the obstacle recognition method based on laser radar is difficult to apply. In addition, the binocular matching of environmental perception technology based on binocular stereo vision has a large amount of binocular matching calculation and slow processing speed, making it difficult to achieve efficient perception. Therefore, how to accurately perceive and identify harsh, complex and unknown extraterrestrial environments under the constraints of limited resources is worthy of further study. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art, propose an autonomous terrain perception method for an extraterrestrial micro-patrol probe, construct a theoretical model of the depth of the detection area, realize obstacle detection using only ranging information at an extremely low viewing angle, and meet the needs of tasks such as star table patrol detection.

[0005] The technical solution of the present invention is:

[0006] A method for autonomously sensing terrain of an extraterrestrial micro-patrol probe, comprising:

[0007] Use the Tof camera to measure the actual depth value of the star catalog in the camera coordinates;

[0008] Based on the imaging principle of a monocular camera, a theoretical model of the depth of the detection area is constructed, and based on the model, the theoretical depth value of the star table in the camera coordinates is calculated;

[0009] Based on the obtained actual depth value and theoretical depth value, design an obstacle detection criterion; detect obstacles in the detection area according to the obstacle detection criterion, and identify the obstacles as protrusions or pits.

[0010] Furthermore, use a Tof camera to measure the actual depth value of the star catalog in the camera coordinates. The actual depth value is:

[0011] The distance value D between any point (i, j) in the star catalog detection area and the camera i,j :

[0012]

[0013] where D i,j is the distance value between any point (i, j) in the star catalog detection area and the camera, that is, the actual depth value; C is the speed of light; λ is the modulation frequency of the signal; Δφ i,j represents the phase difference between the transmitter and receiver of the Tof camera.

[0014] Furthermore, based on the monocular camera imaging principle, construct a depth theoretical model for the detection area. The model is:

[0015]

[0016] In the formula:

[0017]

[0018] where d i,j is the theoretical depth value of any point (i, j) in the star catalog detection area; α int represents the horizontal mounting angle of the camera, h and w respectively represent the image height and width, u represents the pixel size, f represents the focal length, and Height represents the camera mounting height.

[0019] Furthermore, based on the obtained actual depth value and theoretical depth value, the designed obstacle detection criterion is:

[0020] D i,j -d i,j > th1, and the pixel value here is set to A;

[0021] D i,j -d i,j < th2, and the pixel value here is set to B;

[0022] Otherwise, the pixel value here is set to C;

[0023] where D i,j 、d i,jis the actual depth value and theoretical depth value of any point (i, j) in the star catalog detection area, th1 and th2 represent the obstacle judgment thresholds respectively; A, B, and C take values ​​from 0 to 255, A <C<B。

[0024] Furthermore, th1 and th2 are set to 0.05 and -0.05 respectively.

[0025] Furthermore, the values ​​of A, B, and C are 0, 255, and 128.

[0026] Furthermore, through connected domain analysis, it is identified that the area with pixel value A is a pit, and the area with pixel value B is a bulge.

[0027] The advantages of the present invention compared with the prior art are:

[0028] (1) The present invention completes the design of the obstacle detection method in the detection area based on the theoretical model of star table depth measurement, which effectively enhances the perception capability of the micro-rover under limited resources.

[0029] (2) Compared with the existing binocular stereo vision and lidar perception methods, the present invention takes into account constraints such as computing resources and the size and weight of the patrol vehicle, saves energy, and is more suitable for miniaturized patrol detection tasks. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0031] Figure 1 This is a schematic diagram of measuring a star chart using a Tof camera in an embodiment of the present invention;

[0032] Figure 2 The star table obstacle detection result of the embodiment of the present invention;

[0033] Figure 3 This is a flow chart of a method for autonomous terrain perception by an extraterrestrial micro-patrol probe according to an embodiment of the present invention. DETAILED DESCRIPTION

[0034] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0035] The present invention proposes a method for autonomous terrain perception of an extraterrestrial micro rover detector, as follows: Figure 3 As shown below, the specific steps are as follows:

[0036] S1: Use a Tof camera to measure the actual depth value of the star surface in the camera coordinates, as shown below: Figure 1 As shown below.

[0037] The distance value D between any point (i, j) in the star surface detection area and the camera is: i,j :

[0038]

[0039] In the formula: C is the speed of light; λ is the modulation frequency of the signal; Δφ i,j represents the phase difference between the transmitter and receiver of the Tof camera.

[0040] S2: Based on the monocular camera imaging principle, construct a theoretical depth model for the detection area. The depth information at any point (i, j) in the star surface detection area is:

[0041] In the formula:

[0042]

[0043] In the formula:

[0044]

[0045] α int represents the horizontal mounting angle of the camera, h and w respectively represent the image height and width, u represents the pixel size, f represents the focal length, and Height represents the camera mounting height.

[0046] S3: Obstacle detection and recognition: Use the actual depth value measured by the Tof camera and the calculated value of the theoretical model to design an obstacle detection criterion; finally, detect the obstacles in the detection area according to the obstacle detection criterion and identify the obstacles as protrusions or pits. Based on the depth calculation in the detection area, by comparing and determining the true depth value D

[0047] at different detection positions (i, j) and the theoretical value d i,j and i,j size, determine the obstacle area and complete the obstacle detection.

[0048] (3.1) If D i,j - d i,j > th1, set the pixel value here to 0;

[0049] (3.2) If D i,j - d i,j < th2, set the pixel value here to 255;

[0050] The pixel values ​​of the remaining image points are set to 128.

[0051] Wherein: th1 and th2 represent the threshold values ​​respectively.

[0052] Through connected domain analysis, it is identified that the area with a pixel value of 0 is a pit, and the area with a pixel value of 255 is a bulge.

[0053] The present invention will be further described below by way of examples:

[0054] The camera installation height is 0.15m, and the camera horizontal installation angle is α int is 28.5°, the image height h is 480, the image width w is 630, the pixel size u is 0.0043m, and the camera focal length f is 1.93m.

[0055] Construct a depth measurement model for the detection area:

[0056] The distance D between any point (i, j) in the star catalog detection area and the camera i,j :

[0057]

[0058] Where: C is the speed of light; λ is the modulation frequency of the signal; Δφ i,j Tof represents the phase difference between the camera transmitter and the receiver.

[0059] Construction of theoretical model for detection area depth:

[0060] The depth information at any point (i, j) in the star catalog detection area is:

[0061]

[0062] Where:

[0063]

[0064] α int represents the horizontal installation angle of the camera, h and w represent the image height and width respectively, u represents the pixel size, f represents the focal length, and Height represents the camera installation height.

[0065] Obstacle detection and recognition:

[0066] Based on the depth calculation of the detection area, the true depth value D at different detection positions (i, j) is determined by comparison i,j and the theoretical value d i,j size, determine the obstacle area, and complete obstacle detection.

[0067] (3.1) If D i,j -d i,j>th1, the pixel value is set to 0 here;

[0068] (3.2) If D i,j -d i,j <th2, the pixel value is set to 255 here,

[0069] In the formula: th1 and th2 respectively represent thresholds, and the values are 0.05 and -0.05 respectively. The pixel values of the remaining image points are set to 128.

[0070] By adopting four-connected domain analysis, the area with a pixel value of 0 is identified as a pit, and the area with a pixel value of 255 is identified as a protrusion.

[0071] The above-described embodiments are only relatively preferred specific embodiments of the present invention. The ordinary changes and substitutions made by those skilled in the art within the scope of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for autonomous terrain perception of an extraterrestrial micro-patrol probe, characterized in that: include: Use the Tof camera to measure the actual depth value of the star catalog in the camera coordinates; Based on the imaging principle of a monocular camera, a theoretical model of the depth of the detection area is constructed, and based on the model, the theoretical depth value of the star table in the camera coordinates is calculated; Based on the actual depth value and theoretical depth value obtained, the obstacle detection criterion is designed; Obstacles in the detection area are detected according to obstacle detection criteria, and the obstacles are identified as protrusions or pits.

2. The method for autonomous terrain perception of an extraterrestrial micro-patrol probe according to claim 1 is characterized in that: The actual depth value of the star table in the camera coordinates is measured using a Tof camera. The actual depth value is: The distance D between any point (i, j) in the star catalog detection area and the camera i,j : Among them, D i,j is the distance between any point (i, j) in the star map detection area and the camera, that is, the actual depth value; C is the speed of light; λ is the modulation frequency of the signal; Δφ i,j Tof represents the phase difference between the camera transmitter and receiver.

3. The method for autonomous terrain perception of an extraterrestrial micro-patrol probe according to claim 1 is characterized in that: A theoretical model of detection area depth is constructed based on the imaging principle of a monocular camera. The model is: Where: Among them, d i,j The theoretical depth value of any point (i, j) in the star catalog detection area; α int represents the horizontal installation angle of the camera, h and w represent the image height and width respectively, u represents the pixel size, f represents the focal length, and Height represents the camera installation height.

4. The method for autonomous terrain perception of an extraterrestrial micro-rovers according to claim 1 is characterized in that: Based on the actual depth value and theoretical depth value obtained, the obstacle detection criterion designed is: D i,j -d i,j >th1, where the pixel value is set to A; D i,j -d i,j <th2, where the pixel value is set to B; Otherwise, the pixel value here is set to C; Among them, D i,j ,d i,j is the actual depth value and theoretical depth value of any point (i, j) in the star catalog detection area, th1 and th2 represent the obstacle judgment thresholds respectively; A, B, and C take values ​​from 0 to 255, A <C<B。 5. The method for autonomous terrain perception of an extraterrestrial micro-patrol probe according to claim 4 is characterized in that: The values ​​of th1 and th2 are 0.05 and -0.05 respectively.

6. The method for autonomous terrain perception of an extraterrestrial micro-patrol probe according to claim 4 is characterized in that: The values ​​of A, B, and C are 0, 255, and 128.

7. The method for autonomous terrain perception of an extraterrestrial micro-rovers according to claim 4 is characterized in that: Through connected domain analysis, it is identified that the area with pixel value A is a pit, and the area with pixel value B is a bulge.

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